1. Field of the Invention
The present invention relates to an optical fiber amplifier for directly amplifying signal light in an optical communication system and, more particularly, to an optical amplifier used in wavelength division multiplex communication.
2. Related Background Art
As conventional optical fiber amplifiers, arrangements based on various pumping schemes have been developed. A conventional optical amplifier is disclosed in "Optical Amplifier and Its Applications", OHMSHA, LTD., edited by Hideki Ishio, pp. 111.